High-voltage circuit breaker with gas quenching

ABSTRACT

A HIGH-VOLTAGE CIRCUIT BREAKER HAS A SEALED UNPARTITIONED METAL TANK CONTAINING ONE OR MORE SETS OF SELF-BLAST BREAKING CHAMBERS OR INTERRUPTERS IN AN ENVIRONMENT OF SULFUR HEXAFLUORIDE (SF6) AT A PRESSURE OF 3-5 KG./CM.2. THE MEDIUM SERVES AS THE BLAST GAS AS WELL AS THE ELECTRICAL INSULATION FLUID FOR THE VARIOUS PARTS OF THE SWITCHES.

Jan. 23, 1973 a. J, cALvl'No y TEIJEIRO HIGH-VOLTAGE CIRCIUT BREAKER WITH GAS QUENCHING Filed March 22, 1971 5 Sheets-Sheet l FIG.I

INVENTOR ATTORNEY 1973 B, J, cALVIN y TEIJEIRO ,71

HIGH-VOLTAGE CIRCI-UT BREAKER WITH GAS QUENCHING Filed March 22, 1971 5 Sheets-Sheet 2 FIG.2

a. J. cALvlfio y TEIJEIRO ATTORNEY Jan. 23, 1973 B. J. cALvlfio y TEIJEIRO 3,7

HIGH-VOLTAGE CIRCIUT BREAKER WITH GAS QUENCHING Filed March 22, 1971 .5 Sheets-Sheet 5 lOlb a..1. CALVI'N'O TEIJEIRO a mvEm oR.

ATTORNEY United States Patent 3,712,969 HIGH-VOLTAGE CIRIIUIT BREAKER WITH GAS QUENCHING Benito lose Calvino y Teije'n'o, Ber-game, Italy, assignor to Magrini Fabbriche Riunite Magrini Scarpa e Magnano M.S.M. S.p.A., Milan, Italy Filed Mar. 22, 1971, Ser. No. 126,788 Claims priority, application Italy, Apr. 7, 1970, 22,980/70 Int. Cl. H01l1 33/70 U.S. Cl. 200-148 R Claims ABSTRACT OF THE DISCLOSURE A high-voltage circuit breaker has a sealed unpartitioned metal tank containing one or more sets of self-blast breaking chambers or interrupters in an environment of sulfur hexafluoride (SP at a pressure of 3-5 kg./cm. The medium serves as the blast gas as Well as the electrical insulation fluid for the various parts of the switches.

(l) FIELD OF THE INVENTION My present invention relates to high-voltage circuit breakers and, more particularly, to a circuit breaker in which sulfur hexafluoride (SP constitutes the quenching and insulating medium.

(2) BACKGROUND OF THE INVENTION A large number of high-voltage circuit-breaker designs have been proposed in recent years, as the problem of power distribution and power requirements increase with increasing population and industrialization.

Circuit breakers are known of many types but generally can be considered to comprise a pair of electrodes or contacts, at least one of which is movable, an insulating or dielectric fluid adapted to flood the gap between the contacts when the circuit breaker is opened, a mechanism for actuating the movable contact, and means for quenching the circuit-breaking are which is formed at high voltages when the movable contact is withdrawn from engagement with the fixed contact.

It is known, for example, that the circuit-breaking arc may be disrupted, broken or attenuated by sweeping the space between the contacts free from ionized particles and thereby reducing the conductivity of the gap. This may be accomplished by a blast of the fluid, which may be a liquid (e.g. oil) or gas such as air or sulfur hexafluoride, the latter having particularly suitable qualities in this regard. Circuit-breaker designs may include magnetic or gas-blast systems for assisting in the dissipation or breakdown of the arc, e.g. by elongating it to the point that the voltage is no longer able to sustain the discharge, especially as the amplitude of the current passes through zero in the case of alternating-current switches.

More specifically, circuit breakers have been provided heretofore with metal housings, enclosures or tanks containing one or more sets of interrupter contacts, the metal enclosure being mounted upon a rolling carriage to enable servicing of the circuit breaker. It is a common practice, in connection with such circuit breakers, to provide two sets of series-connected contacts for each pole of the circuit to be controlled. The interior of the housing may be subdivided into breaking chambers in which respective arcs are generated between sets or pairs of contacts and the systems have been operated in various modes.

It has already been pointed out that liquiddielectric circuit breakers may be provided in which oil or some other liquid having high resistivity and a high breakdown voltage, are provided around the sets of contacts and/or serve as an arc-quenching means. In another mode of operation, a dielectric gas, such as the sulfur hexafluoride ice serves as an insulating fluid between the metal housing and the contacts, while the oil or dielectric liquid constitutes the arc-quenching fluid. In a third variant, compressed air only may be provided for insulating the sets of contacts from the metal housing or casing and for sweeping the gap between the contacts free from ionizable .or ionized particles and thereby quenching the arc. For

example, air at a pressure of 5 kg. per cm. may fill the housing to form the insulating fluid, while compressed air at a pressure of 25 kg. per cm. is forced through the breaking chamber when the contacts are opened to produce a quenching axial blast of air which is released into the atmosphere.

It will be apparent that systems of the latter type are disadvantageous because two fluid systems are necessary to maintain the pressure levels for insulation and quenching. The problem is complicated even further when one of the fluids is replaced by a gas such as sulfur hexafiuoride, since the problem of supply of the several fluids is produced.

In substantially all of the aforedescribed system, moreover, repeated operation of the circuit breaker results in the formation of decomposition products and are residues which contaminate the fluids; it is thus important under these circumstances to maintain a separation between the arc quenching fluid which is predominantly contaminated, and the insulating fluid which should remain free from contamination for long service life. Then it is only necessary to dispose of the contaminated fluid from the breaking chamber. In this connection also, one might mention that contamination of the insulating fluid, for example, may result in a reduction of its breakdown potential and lead to arcing between the contacts and other portions of the switch, e.g. the housing.

Finally, it is to be observed that conventional circuitbreaker assemblies for high-voltage applications have hitherto been complex, costly, complicated to operate and maintain and prone to breakdown.

(3) OBJECTS OF THE INVENTION It is, therefore, the general object of the present invention to provide an improved circuit breaker for high-voltage applications which obviates the difliculties mentioned above.

It is another object of the invention to provide a high voltage circuit breaker of the metal-enclosed type which is of simpler construction, affords greater ease of maintenance, is more efiicient, is less susceptible to breakdown and is of lower cost than earlier systems of the same general character.

A further object of this invention is to provide an improved circuit-breaker assembly for high-voltage systems which uses a single fluid as the insulating and arc-quench ing medium, preferably sulfur hexafluoride (SF gas.

Still further, it is an object of my invention to provide an improved circuit breaker of the general class described which is less prone to failure as a result of the production of decomposition products with repeated opening and closing of the breaker contacts.

In a further object of the invention, the circuit breaker 0f the present invention is to be more quiet and compact, less expensive and of smaller dimensions than circuit breakers of equivalent electrical parameters as may have been proposed heretofore.

(4) SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, in a circuit-breaker assembly, which comprises a metal housing or tank mounted upon a rolling support or carriage and provided with a single inner chamber in which a plurality of sets of contacts are mounted, a mechanism being located externally-of this chamber and connected to the movable contact of each set for actuating same. The hermetically sealed chamber receives as the insulating medium and the quenching medium, sulfur hexafiuoride (SP gas which may pass freely around and through the breaking chambers associated with each set of contacts. The interior of the tank is thus free from any internal partitions, shutters or significant constrictions between the regions of the respective sets of contacts.

More specifically, each set of contacts and the associated breaking chamber is of the low-pressure and axial selfblasting type, provided with nozzles and orifices described for example in the commonly assigned copending application Ser. No. 25,144 filed Apr. 2, 1970 and at pages 81-83 of the I.E.E.E. Spectrum, September 1970 (volume 7, Number 9). In these contact sets, breakers or interrupters, no residual decomposition products are formed which pollute the sole gaseous fluid serving as the insulating medium and the arc-quenching medium.

According to a more specific feature of this invention, each interrupter set is mounted in the tank at opposite ends via electrical insulators having high dielectric strengths and forming an openwork through which the sole gaseous medium can circulate around the breaker sets and between the latter and the walls of the housing and the actuating mechanism for the movable contacts.

According to a further (feature of this invention, the housing or tank is elongated in the direction in which the interrupter sets extend and the interrupter sets are centered in the housing which may be rotationally symmetrical, atleast in part, about the axis of each interrupter set. At opposite ends of the interrupter sets, the insulators mentioned earlier are provided with and traversed by conductive rods forming terminals or plugs for the connection of the system into the circuit. Preferably, the insulators are frustoconical and converge inwardly from the wall of the housing through which the contact rods or plugs emerge and have broad bases flanged to the housing around the window through which each plug projects. The windows, moreover, may be provided with flanges (for securing the circuit breaker to the housing of the apparatus to be connected therewith.

FIG. 3 is a view similar to FIG. 1 showing another In FIGS. 1 and 2 of the drawing, I have shown a circuitbreaker assembly which comprises a metal enclosure 01' housing tank 1 mounted upon a carriage 1a having a support structure 1b and 1c forming mounts for ancillary equipment. The sheet-metal housing 1 also comprises a tubular body 1d of generally oval configuration (FIG. 2) with generally cylindrical portions 1e and 1 for each breaker set or interrupter 4.

Each breaker set 4 comprises a fixed contact 2 and a movable contact 3 altogether being part of a self-quenching gas-blast breaker for examples as described in the aforementioned copending application. The tank 1 is held at ground potential and consequently can be manipulated by the operator without difficulty. In addition, it defines a single chamber 1g, all parts of the interior of which are in fiuid communication and filled with a gaseous fluid having a high dielectric constant and breakdown voltage, especially sulfur hexafluoride. The right-hand side of the tank 1 is provided with extensions 1h and 1i whose flanges 1j and 1k are connected hermetically to a cover 1m and In respectively. An extension 1p and lq of each cover forms an anteroom for respective levers 10a and 10b of a mechanism generally represented at 10 for actuating the movable contacts.

Each interrupter set 4 has a generally horizontal axis 4a or 4b, which defines a vertical plane P constituting a median plane or a plane of symmetry of the housing 1. Furthermore, the axes 4a and 4b, and the plane P are perpendicular to a vertical plane P of the opposite side of the housing 1 in which each cylindrical compartment -1r or 1s extending from housing portions 1e and 1 is formed with a flange 5.

The latter may be bolted to corresponding flanges of a transformer housing or other unit to be coupled'with the switch of the present invention.

According to still another feature of this invention, the

windows lie in a common vertical plane while the plugs extend perpendicularly thereto and lie horizontally but, advantageously, in a second vertical plane perpendicular to the first and coinciding with a vertical plane of symmetry of the housing. When the breaker sets are also horizontal, therefore, they can be electrically connected by a bus bar within that housing and have corresponding extremities terminating in the aforementioned plugs. Where a single set of contacts is provided for each pole Oif the electrical circuit the opposite ends of the breaker contacts terminate in the aforementioned horizontal plugs but the contacts and the breaking chamber are oriented vertically. The mechanism for actuating the movable contacts advantageously includes a fluid-responsive system mounted upon the rolling carriage and connected by a linke-and-lever arrangement to the movable contacts, a compressor and supply tank being likewise mounted upon the carriage to provide the fluid for actuating the break. The housing may be provided at its end proximal to the movable breaker contact, with an antechamber in which a respective lever is journaled for coupling to the movable contact.

,(5) DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a vertical cross-sectional view through a circuit breaker assembly according to the present invention;

FIG. 2 is an endview thereof; and

The interrupter sets 4 are supported by inwardly converging frustoconical insulators 6a, 6a and 6 b, 6b, respectively, the broad bases'of these insulators being bolted to inwardly extending flanges 1! of the housing. The narrow bases of the frustoconical insulators 6a and 6b fixedly receive the contacts 2. while the narrow bases of insulator 6a and 6b are formed with sliding guides 6a and 6b for plungers 3a and 3b of the moving contacts 3 mentioned earlier. These plungers are articulated to respective links 10c and 10d which, in turn, are pivotally connected to the free ends of the levers 10a and 1012 within the antechambers 1p and lq. Shafts of these levers as seen at 9 in FIG. 2, extend through the wall of the housing via seals la and are connected to levers 10e and 10], respectively tied by a rod 10g to a bellcrank lever 10h hinged at 10f to a portion of the housing externally thereof. A bar -10j connects the arm of the latter bellcrank lever to a pneumatically operated actuator 8 within a compartment 1v beneath the tank *1.

Each of the bell-shaped standoff insulators 6 is provided with large cross-section openings or windows 13 affording communication between the chamber 1g and the spaces within the insulators without significant constriction of the flow passage between these spaces. Hence the insulators 6 impose no barrier between the various sections of the tank which may be separated from one another by the insulators. While the insulators 6, i.e. the individual insulators 6a, 6b, 6a and 6b, can be of any dielectric material capable of sustaining, without breakdown or significant leakage, the voltages applied between the contact 7 and ground potential, it has been found to be advantageous to make them of a ceramic, glass or porcelain which is capable of providing the mechanical support for the contact 7 as well as the desirable electrical characteristics and a freedom from attack by the fluid within space 1g (i.e. sulfur hexafluoride).

The mouths 14 of each tank section in plane P are circular, as noted earlier, and provided with the flanges 5 for connection of the unit shown in the drawing to the other electrical equipment of the plant in which it is used. Such other electrical equipment may include a transformer housing represented at T and having a flange F to which the flanges 5 may be bolted. The housing terminal is a tulip S which fits over and hugs the plug member 7 of the associated set of contacts. In other Words, members 7 constitute connection terminals passing through the mouths 14 from each interrupter set 4 in the tank 1. The terminals 7 lie along the axis 4a and 4b and terminate short of the plane P at which the housing of the circuit breaker is joined to the housing T of the other equipment. Terminals 7 are merely outward extensions of the fixed contacts 2 and are supported by the bell-shaped insulators 6a and 612 so as to be centered precisely in the circular mouths 14 through which they pass. While tulip-type sockets are preferred for connecting the circuit breaker of the present invention in the electrical system of the plant, any other socket formation or female connector may be used for this purpose.

The mouths 14 have a cross section equal at least to the cross section of the large base of the bell-shaped insulators 6a and 6b and hence provide a large-diameter path unoccupied by the respective terminal 7 through which the fluid (SP which fills tank 1 can freely circulate to and through the circuit equipment of the plant and its respective housing.

While the insulators 6a and 6b etc. shown in FIGS. 1 and 2 are provided with openings to permit throughflow of the insulating and dielectric fluid, sulfur hexafiuoride, these insulators may also be closed to form a hermetic seal with the tank, in which case the insulating gas within the tank 1 is isolated from the other equipment and removal of the tank 1 and the circuit breaker from the other equipment does not result in loss of the insulating gas within the system. In addition, flap-type valves such as that shown at V in dot-dash lines may be provided over the openings 13 to close the chamber 1g when the circuit breaker is removed from the other equipment. In the latter case, removal of the circuit breaker limits the loss of the insulating fluid.

Alternatively, insulators 6a and 6b along the connection side of the housing will not be provided with openings while the insulators 6a and 6b on the actuating mechanism side of the housing are provided with openings 13. In this arrangement, there is no loss of the sulfur hexafluoride when the circuit breaker is disconnected from the other equipment, but the sulfur hexafluoride nevertheless fills the spaces around the actuating mechanism to constitute an insulating medium. The flaps V may be spring-biased to close the holes 13 and may be connected with a mechanism represented diagrammatically at M which opens each flap when the apparatus of the present invention is bolted to the remaining equipment.

The carriage supporting the tank is provided with wheels 16 which enable displacement of the circuit breaker assembly along the ground to facilitate removal from or connection to the other plant equipment and repair or maintenance of the circuit breaker.

In the drawing, I have shown a single circuit-breaker pole only and it should be understood that a three-phase system, for example, will require three breaker-poles, each having two sets of contacts 4 in series as has been illustrated. All six sets of breaker contacts may be provided in a single housing with appropriate insulators, terminals, etc. or in separate housings I mounted upon a common chassis or carriage. In addition, more than two sets of contacts may be connected in series, should the voltage level require it. In general, the system of the present invention as illustrated in FIGS. 1 and 2-, permits switching of voltages of the order of hundreds of kilovolts. Regardless of how many contact sets are provided I prefer to use only a single connection mouth and flange for each side of the circuit breaker so that there will always be two such mouths and a corresponding number of flanges. Moreover, the actuating mechanism 8, 10, etc. will generally be connected to all of the moving contacts.

Below the tank 1, I also provide a compressed-air reservoir 11 and a motor-compressor set 12 which generates the air pressure within the tank 11 for operating the control device 8. The control device is of conventional construction. Within the vessel 1, a bus bar 17 connects the movable contacts 3 of the sets of contact, thereby placing the system in series.

The compartment 1g is filled with sulfur hexa-fiuoride gas at a pressure of 3-5 kg./cm. and the contact sets are of the self-blast type as described in the copending application mentioned earlier. Consequently, when the control mechanism 8 is actuated, rod 10 is shifted to the left, rod 10g moved downwardly, and levers 10a and 10b swung in the clockwise sense. The rods 10c and 10d are shifted to the right and the contacts are open, thereby forcing the sulfur hexafluoride gas to the breaker chamber. Since the sulfur hexafluoride has a density from 5-6 times greater than the density of air, leakage is minimized, although such leakage is at any rate minimal because of a small number of seals. The sulfur hexafluoride constitutes both the insulating medium and the quenching medium. It is to be noted that, since the blast occurs at low pressure, sound problems are eliminated. Furthermore, the single low-pressure fluid reduces complexities of high pressure circuits etc. and the entire system is highly compact, uses a minimum of copper, and reduces energy losses in the Joule effect. The condensers 15 which bridge the contacts can be conveniently mounted as shown in FIG. 1 in the vertical plane of symmetry P In FIG. 3, I have show another circuit breaker embodying the invention wherein, however, only a single set of contacts is provided for each pole. In this case, the carriage 101a is mounted upon wheels 116 but is provided with a platform 1012) upon which the motor-compressor arrangement 112, the tank 111 and the control mechanism 108 are mounted. A further platfiorm 101a receives the tank 101 which is filled with sulfur hexafluoride and this embodiment is generally upright so that the axis 104a of the cylinder coincides with the axis of the set of contacts 104. In this embodiment, the fixed contact 102 is connected with a terminal 107 which extends transversely to the axis 104a through a bell-shaped insulator 106 of the type previously described. The terminal 107 extends coaxially in the mouth 114 of the housing 101 which is surrounded by a flange 105 allowing the apparatus to be secured to the other equipment as previously described. In this embodiment, the axis 107a and 10712 of the terminals 107 and 107 lie in a vertical plane of axis 104a, coinciding with the vertical median plane or plane of symmetry lot the tank.

The movable contact 103 is provided with a plunger 103a which is connected to the terminal 107 extending coaxially in the window 114' which is also surrounded by a flange 105. A bell-shaped standoff insulator 106 is provided for this terminal 107' as well. The plunger 103a is connected by the rod a to the lever 11011 IOf the actuating means. A shaft 109 of this lever runs through the wall of the antechamber 101d (hermetically sealed) to a lever 1100 connected externally of the tank 101 to the actuating rod 110. It will be apparent that this apparatus operates in accordance with the principles already disclosed.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

1. A high-voltage circuit breaker comprising a sealed metal housing defining a single chamber; at least two self-blast breaker sets mounted in said housing and each having at least one movable contact displaceable to force a quenching gas through each breaker set upon circuiting thereof; and actuating means externally of said chamber and link means connecting said actuating means to said movable contacts, said chamber being filled with gaseous sulfur hexafluoride at a pressure of 3 to 5 kg/cm? constituting an insulator between said sets and said housing and forming a quenching medium upon actuation of said movable contact, and means connecting said chamber to a gas-filled electrical device for passing of said gaseous sulfur hexafiuoride therebetween.

Z. A high-voltage circuit breaker comprising: a sealed metal housing defining a single chamber; at least two self-blast breaker sets mounted in said housing and each having at least one movable contact displaceable to force a quenching gas through each breaker set upon open circuiting thereof; and

actuating means externally of said chamber and link means connecting said actuating means to said movable contacts, said chamber being filled with a single dielectric gas constituting an insulator between said sets and said housing and forming a quenching medium upon actuation of said movable contact, said housing being provided with at least two circular windows in a common vertical plane, said breaker set including a pair of terminals extending coaxially with said windows for connection of the circuit breaker to another electrical device, each of said windows being surrounded by a connection flange adapted to be secured to said other device.

3. The circuit breaker defined in claim 2, further comprising at least one genera-11y frustoconical insulator having a large base secured to said housing around a respective window and a small base receiving the respective terminal While supporting said, breaker set.

4. The circuit breaker defined in claim 3 wherein at least one of said insulators is provided with an opening permitting passage of said gas from said chamber to said other device and vice versa upon connection of the circuit breaker to said other device.

5. The circuit breaker defined in claim 4 wherein two such breaker sets are provided in said chamber, further comprising means in said chamber for connecting said breaker sets electrically in series, said link connecting the movable contacts of both breaker sets to said actuating means.

6. The circuit breaker defined in claim 4., further comprising a wheeled carriage carrying said housing, said actuating means including a pneumatic control device mounted on said carriage, a motor-compressor mechanism mounted on said carriage, and a compressed air reservoir connected with said mechanism and with said control device for operating same.

7. The circuit breaker defined in claim 6 wherein said housing is a tank having a vertical axis of symmetry and composed .at least in part of cylindrical portions, said windows being disposed one above the other in a common vertical plane perpendicular to the plane of symmetry.

8. The circuit breaker defined in claim 7 wherein said breaker set lies along said plane of symmetry.

9. A high-voltage circuit breaker comprising:

a sealed metal housing defining a single chamber and provided with two ports connectable to an ancillary electrical device, said housing being filled with a dielectric gas at substantially constant temperature and pressure;

two substantially identical self-blast circuit breaker sets mounted in said housing and each substantially in alignment with a respective port, each breaker set having a stationary contact fixed in said housing and at least one axially movable contact displaceable into and out of engagement with its stationary contact to force said dielectric gas through the respective set;

at least one condenser in said housing extending parallel to and connected electrically in parallel across the contacts of each breaker set;

actuating means externally of said chamber and mounted on said housing for displacement of said movable contacts;

respective link means for connecting said actuating means to each of said movable contacts; and

a pneumatic control means externally of said chamber for powering said actuating means.

10. The circuit breaker defined in claim 9 wherein said ports each consist of a circular window in said housing, said windows lying in a common plane thereof perpendicular to said breaker sets and said condensers, said contacts of each lbreaker set extending along the axis of the respective window, respective outwardly projecting flanges framing each of said windows and connectable to a housing of said other electrical device to enable free circulation between the circuit breaker housing and the housing of said device of said dielectric gas, a respective inwardly converging frustoconical insulator connected to said housing of said circuit breaker at a large base around each window and having a small base carrying coaxially with the window one of the contacts of the respective breaker set, said insulators each having openings permitting the passage of said dielectric gas therethrough, said housing including a wheel carriage supporting said chamber, said control means being mounted on said carriage below said chamber.

References Cited UNITED STATES PATENTS 3,287,531 11/1966 Yonezawa et al. 200l44 AP 3,406,269 10/1968 Fischer 200-148 G 3,562,460 2/ 1971 Koerner 200-448 B 3,566,054 2/1971 Bankan 200148 B 3,603,752 9/1971 [Frink 200-50 AA X ROBERT S. MACON, Primary Examiner US. Cl. X.R. 200148 A 

